Electronic mail server, electronic mail delivery relaying method, and computer program

ABSTRACT

An electronic mail server includes an unsolicited site database for storing a part or a whole of a URL of a Web site that delivers undesired information to a user, a mail reception portion for receiving electronic mail sent by a terminal device of a delivering trader of direct mail, an unsolicited bulk electronic mail decision portion for deciding whether or not the received electronic mail contains a part or a whole of the URL stored in the unsolicited site database, and a mail transmission portion for sending the electronic mail to a terminal device of the user only when it is decided that the received electronic mail does not contain a part or a whole of the URL.

TECHNICAL FIELD

The present invention relates to an electronic mail server that performsa process for preventing unsolicited electronic mail from being sent toa terminal device of a user.

BACKGROUND ART

A delivery of direct mail by electronic mail has, following merits for atrader. First, compared with a delivery by mail or a delivery service,it requires a low cost for delivery and little manpower for deliveringto a lot of users. In addition, the trader can enter a URL of a Web pageof his or her Web site in the electronic mail so that interested userscan access the trader's Web site. Thus, the trader can make theelectronic mail readily without any special consideration about a designor a layout of the electronic mail. Because of these merits, a lot oftraders deliver direct mail by electronic mail.

However, in many cases receiving such electronic mail is inconvenienceto a user. A user may be required to make time to read the electronicmail and to decide whether it is necessary electronic mail or not. Insome cases the user has to access a Web site in accordance with a URLincluded in the electronic mail for deciding whether it is necessaryelectronic mail or not. In addition, there is a case where the contentsof the electronic mail are unpleasant to the user. Furthermore, a userof a cellular phone may have to pay for a communication charge everytime when receiving electronic mail. In this case the communicationcharge increases.

There is proposed a method of refusing to receive electronic mail from aspecific trader designated by the user. For example, a user registers anelectronic mail address or a domain name of the trader who has sentdirect mail many times to the user in an electronic mail server of anInternet service provider. The electronic mail server filters electronicmail to the user to extract electronic mail sent from the trader. Then,the electronic mail server regards the extracted electronic mail asunsolicited bulk electronic mail, which is removed without sending themto a terminal device of the user.

However, an increasing number of traders deliver such unsolicited bulkelectronic mail by falsifying the electronic mail address of sender.Such traders think it is sufficient to inform users of the URL of his orher Web page. As a result, even if the user registers the electronicmail address of the trader in the electronic mail server, suchunsolicited bulk electronic mail can pass the filter and are deliveredto the terminal device of the user.

An object of the present invention is to provide an electronic mailserver and a method that enables a user to refuse to receive unsolicitedbulk electronic mail regardless of an electronic mail address of asender.

DISCLOSURE OF THE INVENTION

An electronic mail server according to the present invention, which isan electronic mail server for relaying electronic mail, includes anunsolicited URL storage portion for storing a part or a whole of a URLof a Web site that delivers undesired information for a receiver ofelectronic mail; a reception portion for receiving electronic mail sentfrom a terminal device of a sender; a decision portion for decidingwhether or not the received electronic mail contains a part or a wholeof the URL stored in the unsolicited URL storage portion; and atransmission portion for sending the received electronic mail to aterminal device of a destination address of the received electronic mailonly when it is decided that the received electronic mail does notcontain a part or a whole of the URL.

Preferably, the electronic mail server includes a URL rule storageportion for storing URL rule information that indicates a relationshipbetween a domain name of a domain when determining a URL and a site nameof a Web site that is provided to each domain; a first reception portionfor receiving unsolicited bulk electronic mail from a terminal device ofa user, the electronic mail being unsolicited electronic mail to theuser who received the electronic mail; a domain extraction portion forextracting a domain name indicated in a URL contained in the receivedunsolicited bulk electronic mail; a Web site specifying portion forspecifying a Web site that delivers a Web page indicated in the URLcontained in the received unsolicited bulk electronic mail by referringto the URL rule information based on the extracted domain name; anunsolicited site storage portion for storing the extracted domain nameand a site name of the specified Web site as unsolicited siteinformation in connection with the user; a second reception portion forreceiving electronic mail sent from a terminal device of a sender; anunsolicited bulk electronic mail decision portion for deciding whetheror not the received electronic mail is unsolicited bulk electronic mailby deciding whether the URL contained in the received electronic mailcontains a domain name and a site name indicated in the unsolicited siteinformation of the user of the destination address of the receivedelectronic mail; and a transmission portion for sending the receivedelectronic mail to a terminal device of a user of the destinationaddress only when it is decided that the received electronic mail is notunsolicited bulk electronic mail.

Alternatively, the electronic mail server further includes a first Webpage obtaining portion for obtaining a Web page indicated in a URLcontained in the unsolicited bulk electronic mail received by the firstreception portion. If the Web page obtained by the first Web pageobtaining portion contains a code for jumping to other Web pageautomatically, the domain extraction portion extracts a domain name of adomain in which the other Web page is provided, the Web site specifyingportion specifies a Web site that delivers the other Web page, and theunsolicited site storage portion stores a domain name of a domain inwhich a Web site is provided for delivering the other Web page and asite name of the Web site as the unsolicited site information.

Alternatively, the electronic mail server further includes a second Webpage obtaining portion for obtaining a Web page indicated in a URLcontained in the electronic mail received by the second receptionportion. If the Web page obtained by the second Web page obtainingportion contains a code for jumping to other Web page automatically, theunsolicited bulk electronic mail decision portion decides whether or notthe electronic mail is unsolicited bulk electronic mail in accordancewith a URL of the other Web page.

A method for relaying electronic mail according to the present inventionincludes the steps of storing a part or a whole of a URL of a Web sitethat delivers undesired information by electronic mail to a receiver;receiving electronic mail sent from a terminal device of a sender;deciding whether or not the received electronic mail contains a part ora whole of the stored URL; and sending the received electronic mail to aterminal device of a destination address of the received electronic mailonly when it is decided that the received electronic mail does notcontain a part or a whole of the URL.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a structure of an electronic mail systemincluding an electronic mail server according to the present invention.

FIG. 2 is a table for explaining an example of a pattern of a rule ofURL.

FIG. 3 shows an example of a hardware structure of the electronic mailserver.

FIG. 4 shows an example of a functional structure of the electronic mailserver.

FIG. 5 shows an example of a structure of a URL rule database.

FIG. 6 shows an example of a structure of an unsolicited site database.

FIGS. 7(a) and 7(b) show examples of electronic mail sent from adelivering trader to a user.

FIG. 8 is a diagram for explaining an example of a general rule of URL.

FIGS. 9(a) and 9(b) show a mechanism of a redirect function of a Webpage.

FIG. 10 shows an example of an HTML file including a redirect code.

FIG. 11 is a flowchart for explaining a flow of process for relayingelectronic mail.

FIG. 12 is a flowchart for explaining a flow of process for registeringan unsolicited site.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, the electronic mail server 1 according to thepresent invention can be connected to terminal devices 2 and 3, a WWWserver 5 and other devices via a communication line 4. The communicationline 4 includes the Internet, a LAN, a private line or a public line,for example.

An electronic mail program for making, sending and receiving electronicmail, a WWW browser for reading Web pages and other programs areinstalled in the terminal device 3. A user of each terminal device 3 isgiven an electronic mail address. The user can use the electronic mailserver 1 as a SMTP (Simple Mail Transfer Protocol) server and a POP(Post Office Protocol) server for sending and receiving electronic mailwith other users. The terminal device 3 includes a personal computer, aworkstation, a personal digital assistant (PDA) or a cellular phone.

The terminal device 2 is used by a delivering trader who sends directmail by electronic mail at random. The direct mail includesadvertisements of goods or services handled by the delivering trader anda URL of the delivering trader's Web site. Here, such electronic mail isreferred to as “unsolicited bulk electronic mail” or “spam mail”. Thedelivering trader knows electronic mail addresses of many users anddesignates these electronic mail addresses as destinations of electronicmail so as to send unsolicited bulk electronic mail.

An Internet service provider (ISP) or a company is given a domain havinga domain name such as “xxxxx.ne.jp”. One or more WWW servers 5 aredisposed in the domain in accordance with the number of members, thenumber of access times or quantity of information to be delivered. Bythis structure, one or more Web sites (WWW sites) are provided to thedomain.

For example, in a case of an ISP domain, a Web site is provided to eachof the individual members or company members. Each of the Web sites isgiven a sub domain or a directory, and a site name is assigned to it fordistinguishing it from other Web sites.

A way of deciding a uniform resource locator (URL), i.e., a way ofassigning a site name of a Web site is different for each of thedomains, and is roughly divided into patterns as shown in FIG. 2. Forexample, there are a pattern A of the site name that is a sub domainname preceding the domain name like “sub domain name.xxxxx.ne.jp”, apattern B of the site name that is a directory name following the domainname like “xxxxx.ne.jp/directory name”, a pattern C of the site namethat is a directory name like “xxxxx.ne.jp/˜directory name” using “˜”(tilde) as a sign indicating the site name, and a pattern D of the sitename that is a combination of a sub domain name and a directory namelike “sub domain name.xxxxx.ne.jp/directory name”. Note that a WWWserver name may be used instead of the sub domain name in the patterns Aand D.

Concerning a company domain, there may be two cases. In one case, aplurality of Web sites is provided for a head office, branch offices andsubsidiaries. In the other case, only one Web site is provided for acorporate advertisement. In the former case, site names are assigned aspatterns A-D shown in FIG. 2. In the latter case, the domain name isused as the site name (as shown in pattern E).

An owner of a Web site can provide a Web page in his or her Web sitewithout restraint basically. The Web page is described in HTML(Hypertext Markup Language) or XML (Extensible Markup Language). Thedelivering trader of direct mail establishes a Web site as a companymember of an ISP or obtains an original domain for establishing a Website.

The electronic mail server 1 includes a CPU 1 a, a RAM 1 b, a ROM 1 c, amagnetic storage device 1 d and various interfaces as shown in FIG. 3.The magnetic storage device 1 d stores an operating system (OS), an SMTPserver program, a POP server program, a program for detectingunsolicited bulk electronic mail and various data. These programs anddata are loaded into a RAM 1 b as necessity, and the CPU 1 a performsthe programs.

Note that the electronic mail server 1 may be constituted by one servermachine as shown in FIG. 1 or by a plurality of server machines in adistributed manner. For example, there may be a structure in which theSMTP server process and the POP server process are performed bydifferent server machines.

By this structure, the electronic mail server 1 realizes functions of aURL rule database 1D1, an unsolicited site database 1D2, a mail box 1D3,a mail reception portion 101, an unsolicited bulk electronic maildecision portion 102, a mail transmission portion 103, an unsolicitedbulk electronic mail reception portion 104, a domain decision portion105, an unsolicited site determination portion 106, a first redirectpre-obtaining portion 107 and a second redirect pre-obtaining portion108 as shown in FIG. 4.

The URL rule database 1D1 stores URL rule information 71 (71 a, 71 b, .. . ) that indicates a regularity of how to assign a URL for each domainon the Internet as shown in FIG. 5. The mail box 1D3 is provided foreach of users of the terminal devices 3 and stores electronic mail 70sent from the terminal device on the Internet to the user.

The unsolicited site database 1D2 stores unsolicited site information 72(72 a, 72 b, . . . ) for each user indicating Web sites that deliverunnecessary information having no meaning to the user as shown in FIG.6. Hereinafter, such a Web site may be referred to as an “unsolicitedsite”. The registration of the Web site (unsolicited site) in theunsolicited site information 72 is performed in accordance with a URLindicated in the document of the unsolicited bulk electronic mail thatthe user received. The method for registering unsolicited sites will bedescribed later.

A form of the URL of the unsolicited site in the unsolicited siteinformation 72 is different in accordance with the above-mentionedpattern of the domain (see FIG. 5). For example, in the case of a Website that is established in a domain that adopts the pattern A, it isdescribed like “ppp.bbbbb.ne.jp” in a form of “site name (sub domainname)+domain name”. In the case of a domain that adopts the pattern E, awhole domain forms one Web site. Therefore, a site name is describedonly by a domain name like “aaaaa.co.jp”.

The mail reception portion 101 receives the electronic mail 70 that issent to the user of the terminal device 3 among electronic mail sentfrom various terminal devices on the Internet. The electronic mail 70may include unsolicited bulk electronic mail sent from the terminaldevice 2 of a delivering trader of direct mail.

The unsolicited bulk electronic mail decision portion 102 decideswhether the received electronic mail 70 is unsolicited bulk electronicmail or not. The decision is performed as described below. First, a URLincluded in a main body of the electronic mail 70 is extracted. Forexample, in the case of electronic mail 70 a shown in FIG. 7(a),“http://www.ppp.bbbbb.ne.jp/top.html” is extracted.

Then, it is decided whether or not any of the unsolicited sitesindicated in the unsolicited site information 72 of the user in thedestination address of the electronic mail 70 is identical to a whole ora part of the extracted URL. In the case of the electronic mail 70 athat is sent to the user A, “ppp.bbbbb.ne.jp” among five unsolicitedsites indicated in the unsolicited site information 72 a shown in FIG. 6is identical to a part of the extracted URL. If they are identical, itis decided that the electronic mail 70 a is unsolicited bulk electronicmail. On the contrary, if any unsolicited site indicated in theunsolicited site information 72 a is not identical to a whole or a partof any URL in a main body like electronic mail 70 b shown in FIG. 7(b),the electronic mail 70 b is decided to be an ordinary electronic mail.

With reference to FIG. 4 again, the mail transmission portion 103 sendsthe electronic mail 70 that was decided to be an ordinary electronicmail to the terminal device 3 of the user of the destination address. Ifthe terminal device 3 is a cellular phone, the electronic mail 70 issent at the timing when it is decided to be an ordinary electronic mail.If the terminal device 3 is a personal computer, the electronic mail 70is temporarily stored in the mail box 1D3 of the user. Then, it is sentat the timing when a request is made by the terminal device 3.

The electronic mail 70 that was decided to be unsolicited bulkelectronic mail is erased without being sent to the user. However, it ispossible not to erase the electronic mail 70 directly but to store ittemporarily in the mail box 1D3 of the user with distinguished fromordinary electronic mail. Thus, the user can check contents of theunsolicited bulk electronic mail before erasing the same. In this case,the unsolicited bulk electronic mail is erased when the user issues aninstruction or after a predetermined period of time has passed.

The electronic mail 70 that does not include any one of URLs of Websites (unsolicited sites) registered in the unsolicited site information72 may be sent to the terminal device 3 even if it is unsolicited bulkelectronic mail. Therefore, the user can request the electronic mailserver 1 not to send the unsolicited bulk electronic mail thatintroduces such an unsolicited site.

The user can operate the terminal device 3 to transfer the electronicmail 70 (unsolicited bulk electronic mail) received from the deliveringtrader to the electronic mail server 1. For example, the electronic mail70 b shown in FIG. 7(b) is sent.

In the electronic mail server 1, after the unsolicited bulk electronicmail reception portion 104 receives the unsolicited bulk electronic mailfrom the terminal device 3, the domain decision portion 105 extracts adomain name from the URL in this unsolicited bulk electronic mail. Thus,the domain of the Web site (unsolicited site) is decided, which deliversthe Web page indicated by the URL. In general, URLs are assigned by therule as shown in FIG. 8. Therefore, in the case of the electronic mail70 b, the domain name “ddddd.com” is extracted (decided).

The unsolicited site determination portion 106 specifies the Web siteindicated by the URL in the unsolicited bulk electronic mail inaccordance with the URL rule information 71 that corresponds to theextracted domain. In the case of a URL that is in the electronic mail 70b, it is understood that the site name appears after the domain namefrom the URL rule information 71d of the domain “ddddd.com” shown inFIG. 5. Therefore, the Web site is specified to be “abcde”.

The specified Web site is regarded as an unsolicited site for the userthat sent the unsolicited bulk electronic mail and is added (registered)to the unsolicited site information 72 of the user. The Web site(unsolicited site) is registered so as to include a site name and adomain name in accordance with the rule indicated in the URL ruleinformation 71 of the domain that belongs to the Web site. For example,in the case of the above-mentioned Web site “abcde”, it is registeredlike “ddddd.com/˜abcde” in accordance with the URL rule information 71dshown in FIG. 5. However, if only one Web site is formed in one domain,the domain name indicates the site name of the Web site. Therefore, thedomain name is registered like “aaaaa.co.jp” in the unsolicited siteinformation 72.

By the process described above, the user can refuse to receiveunsolicited bulk electronic mail that introduces the URL of theunsolicited site registered in his or her unsolicited site information72.

FIGS. 9(a) and 9(b) show a mechanism of a redirect function of a Webpage, and FIG. 10 shows an example of an HTML file including a redirectcode. Using redirect function of HTML or XML, a delivering trader canmake a user view a trader's Web site without describing the URL of thetrader's Web site in the electronic mail 70 that is delivered to theuser. This is possible by the mechanism illustrated in FIGS. 9(a) and9(b).

For example, the delivering trader delivers electronic mail 70 c asshown in FIG. 9(a). When the URL described in the received electronicmail 70 c is clicked, the terminal device 3 starts the WWW browser anddownloads a Web page 74 (HTML file) from a dummy Web site 5 a as shownin FIG. 9(b). This HTML file includes a tag C1 that is a redirect (jump)code as shown in FIG. 10. Thus, the terminal device 3 accesses(redirects to) the trader's real Web site 5 b so as to download a Webpage 75 in accordance with the tag C1.

The delivering trader makes new dummy Web sites like the Web site 5 aone by one using a so-called free provider and delivers unsolicited bulkelectronic mail to the user while changing the URL shown in FIG. 9(a).Accordingly, the user cannot refuse to receive the unsolicited bulkelectronic mail that introduces indirectly the delivering trader's realWeb site 5 b by registering the Web site 5 a in the unsolicited siteinformation 72 shown in FIG. 6. Therefore, in order to counter thesemeans, the electronic mail server 1 performs the following process.

The first redirect pre-obtaining portion 107 shown in FIG. 4 obtains aWeb page in accordance with the URL described in the electronic mail 70that was sent from the user's terminal device 3. Then, a redirect codeis searched from the obtained Web page. If a redirect code is found, aURL of a destination of the redirect in the code is extracted. Forexample, if an HTML file shown in FIG. 10 is obtained as the Web page, aURL “http://www.ppp.bbbbb.ne.jp/top.html” that is indicated in the tagC1 is extracted.

The domain decision portion 105 decides a domain of the Web site thatdelivers the Web page indicated by the extracted URL. The unsolicitedsite determination portion 106 specifies the site name of this Web site.By these processes, this Web site is regarded as an unsolicited site andis registered in the unsolicited site information 72 of the user whosent the unsolicited bulk electronic mail.

On the other hand, the second redirect pre-obtaining portion 108 obtainsa Web page designated by the URL in a main body of the electronic mail70 sent from the delivering trader. The unsolicited bulk electronic maildecision portion 102 extracts a URL of the destination of redirect froma redirect code described in the obtained Web page (for example the tagC1 shown in FIG. 10). Then, it decides whether the electronic mail 70 isunsolicited bulk electronic mail or not in accordance with the extractedURL and the unsolicited site information 72 of the user of thedestination address. If the electronic mail 70 is decided not to beunsolicited bulk electronic mail, it is sent to the terminal device 3 ofthe user of the destination address. If the electronic mail 70 isdecided to be unsolicited bulk electronic mail, it is erased or storedin the mail box 1D3 only for a predetermined period while distinguishedfrom ordinary electronic mail.

Next, a flow of the process performed by the electronic mail server 1will be descried with reference to flowcharts. FIG. 11 is a flowchartfor explaining a flow of process for relaying electronic mail, and FIG.12 is a flowchart for explaining a flow of process for registering anunsolicited site.

In FIG. 11, when receiving the electronic mail 70 sent by the deliveringtrader to the user A for example (#11), a URL described in thiselectronic mail 70 is extracted (#12), and it is decided whether theelectronic mail 70 is unsolicited bulk electronic mail or not inaccordance with the extracted URL and the unsolicited site information72 a of the user A (#13). If the electronic mail 70 is decided to beunsolicited bulk electronic mail (Yes in #13), it is erased (#19).Otherwise, it is stored in the mail box 1D3 of the user A withdistinguished from ordinary electronic mail to be erased after apredetermined period.

If the electronic mail 70 is decided not to be unsolicited bulkelectronic mail (No in #13), it is sent to the terminal device 3 of theuser A (#18). However, there is a possibility that the electronic mail70 is unsolicited bulk electronic mail that introduces the Web site ofthe delivering trader (the Web site 5 b) indirectly by means shown inFIG. 9(b). Therefore, the following process may be performed before Step#18.

A Web page designated by the URL extracted in Step #12 is obtained(#14), and it is decided whether or not a redirect (jump) code to otherWeb page is included in this Web page (#15).

If such a code is not included, the electronic mail 70 is sent to theterminal device 3 of the user A (#18). If the code is included, a URL ofa destination of the redirect (jump) is extracted from the code (#16).Then, similarly to Step #13, it is decided whether or not the electronicmail 70 is unsolicited bulk electronic mail (#17). In accordance with aresult of the decision, the electronic mail 70 is erased (#19) or issent to the terminal device 3 of the user A (#18).

When registering a Web page (Web site) in the electronic mail 70received by the user as an unsolicited site, a process is performed inthe procedure shown in FIG. 12. When receiving the electronic mail 70 bas shown in FIG. 7(b) from the user A (#21), for example, the electronicmail server 1 extracts the URL “http://ddddd.com/˜abcde/index.html”described in the electronic mail 70 b (#22) and specifies a Web site(unsolicited site) that delivers the Web page indicated by the URL and adomain to which the unsolicited site belongs (#23). Then, theunsolicited site “ddddd.com/˜abcde” is registered in the unsolicitedsite information 72 a of the user A in accordance with a domain name ofthe specified domain and a site name of the unsolicited site (#24).

Before or after or concurrently with the processes of Steps #23 and #24,a Web page designated by the extracted URL in Step #22 (such as an HTMLfile) is obtained (#25). Then, it is decided whether or not the obtainedWeb page includes a code of redirect (jump) to other Web page (#26). Ifsuch a code is included (Yes in #26), similarly to Steps #22-#24, theunsolicited site is registered in the unsolicited site information 72 aof the user A in accordance with the URL indicating a destination of theredirect (#27-#29).

Note that there is a case where a plurality of dummy Web pages havingredirect codes (the Web site 5 a shown in FIG. 9(b), for example) fromthe URL indicated in the unsolicited bulk electronic mail until thefinal unsolicited site (the Web site 5 b shown in FIG. 9(b), forexample). In order to support this case, the process of Steps #15-#17shown in FIG. 11 or the process of Steps #27-#29 shown in FIG. 12 may berepeated until reaching a Web page without redirect (i.e., a finalunsolicited site).

According to this embodiment, the user can refuse to receive electronicmail that the user thinks a spam regardless of the electronic mailaddress of the sender.

Though the unsolicited site information 72 is stored for each user asshown in FIG. 6 in this embodiment, it is possible to store commonunsolicited site information 72 for all users. For example, Web siteswhich many users regard as unsolicited sites may be registered in thecommon unsolicited site information 72. Otherwise, Web sites thatdeliver information against public policy are registered in advance inthe common unsolicited site information 72 by an administrator of theelectronic mail server 1. It is possible to refuse to receiveunsolicited bulk electronic mail effectively by deciding whether or notthe electronic mail 70 is unsolicited bulk electronic mail in accordancewith this common unsolicited site information 72 and the unsolicitedsite information 72 of the user. Especially, a user who is a beginner ofusing the electronic mail server 1 has a small number of unsolicitedsites registered in his or her unsolicited site information 72. However,by using the common unsolicited site information 72, the user can obtainthe effect of this service soon.

The structure of a whole or a part of the electronic mail server 1, theterminal devices 2 and 3, the structure of the databases including theURL rule database 1D1 and the unsolicited site database 1D2, thecontents and the order of the process can be modified if necessary inaccordance with the spirit of the present invention.

INDUSTRIAL APPLICABILITY

As described above, the electronic mail server according to the presentinvention is useful in that it can eliminate wasteful time for checkingunsolicited bulk electronic mail and provide an environment forefficient work by erasing electronic mail that includes a URL of a Webpage registered in the unsolicited site database without sending it tothe terminal device of the user. In addition, as it decides whether ornot electronic mail is unsolicited bulk electronic mail regardless ofthe electronic mail address of the sender, the unsolicited bulkelectronic mail can be erased even a false electronic mail address ofthe sender is indicated in the electronic mail.

1. An electronic mail server for relaying electronic mail, comprising: an unsolicited URL storage portion for storing a part or a whole of a URL of a Web site that delivers undesired information for a receiver of electronic mail; a reception portion for receiving electronic mail sent from a terminal device of a sender; a decision portion for deciding whether or not the received electronic mail contains a part or a whole of the URL stored in the unsolicited URL storage portion; and a transmission portion for sending the received electronic mail to a terminal device of a destination address of the received electronic mail only when it is decided that the received electronic mail does not contain a part or a whole of the URL.
 2. An electronic mail server for relaying electronic mail, comprising: a URL rule storage portion for storing URL rule information that indicates a relationship between a domain name of a domain when determining a URL and a site name of a Web site that is provided to each domain; a first reception portion for receiving unsolicited bulk electronic mail from a terminal device of a user, the electronic mail being unsolicited electronic mail to the user who received the electronic mail; a domain extraction portion for extracting a domain name indicated in a URL contained in the received unsolicited bulk electronic mail; a Web site specifying portion for specifying a Web site that delivers a Web page indicated in the URL contained in the received unsolicited bulk electronic mail by referring to the URL rule information based on the extracted domain name; an unsolicited site storage portion for storing the extracted domain name and a site name of the specified Web site as unsolicited site information in connection with the user; a second reception portion for receiving electronic mail sent from a terminal device of a sender; an unsolicited bulk electronic mail decision portion for deciding whether or not the received electronic mail is unsolicited bulk electronic mail by deciding whether the URL contained in the received electronic mail contains a domain name and a site name indicated in the unsolicited site information of the user of the destination address of the received electronic mail; and a transmission portion for sending the received electronic mail to a terminal device of a user of the destination address only when it is decided that the received electronic mail is not unsolicited bulk electronic mail.
 3. The electronic mail server according to claim 2, further comprising a first Web page obtaining portion for obtaining a Web page indicated in a URL contained in the unsolicited bulk electronic mail received by the first reception portion, wherein if the Web page obtained by the first Web page obtaining portion contains a code for jumping to other Web page automatically, the domain extraction portion extracts a domain name of a domain in which the other Web page is provided, the Web site specifying portion specifies a Web site that delivers the other Web page, and the unsolicited site storage portion stores a domain name of a domain in which a Web site is provided for delivering the other Web page and a site name of the Web site as the unsolicited site information.
 4. The electronic mail server according to claim 2, further comprising a second Web page obtaining portion for obtaining a Web page indicated in a URL contained in the electronic mail received by the second reception portion, wherein if the Web page obtained by the second Web page obtaining portion contains a code for jumping to other Web page automatically, the unsolicited bulk electronic mail decision portion decides whether or not the electronic mail is unsolicited bulk electronic mail in accordance with a URL of the other Web page.
 5. A method for relaying electronic mail in an electronic mail server, comprising the steps of: storing a part or a whole of a URL of a Web site that delivers undesired information by electronic mail to a receiver; receiving electronic mail sent from a terminal device of a sender; deciding whether or not the received electronic mail contains a part or a whole of the stored URL; and sending the received electronic mail to a terminal device of a destination address of the received electronic mail only when it is decided that the received electronic mail does not contain a part or a whole of the URL.
 6. A computer program product for use in a computer for relaying electronic mail, the computer program product comprising: means for receiving electronic mail sent from a terminal device of a sender, means for deciding whether or not the electronic mail contains a part or a whole of a URL of a Web site that delivers information that is undesired for a receiver of electronic mail; and sending the received electronic mail to a terminal device of the receiver of the electronic mail only when it is decided that the received electronic mail does not contain a part or a whole of the URL.
 7. The electronic mail server according to claim 3, further comprising a second Web page obtaining portion for obtaining a Web page indicated in a URL contained in the electronic mail received by the second reception portion, wherein if the Web page obtained by the second Web page obtaining portion contains a code for jumping to other Web page automatically, the unsolicited bulk electronic mail decision portion decides whether or not the electronic mail is unsolicited bulk electronic mail in accordance with a URL of the other Web page. 